In various situations, it is desirable or even medically necessary for patients to self-administer medication away from a doctor's office or professional medical setting. Such medication may take the form of a liquid or reconstitutable liquid drug administered by sub-cutaneous or intramuscular needle injection. Various medical devices have been developed to enable patients to perform these self-injections without the assistance of a medical professional.
An example of an injection device is shown in U.S. Pat. No. 5,616,132. This patent discloses a portable medicant injection device with a needle that moves when pressurized gas is released into a housing. The user presses downwardly on the device to release the gas, which forces a diaphragm downwardly, carrying the needle with it. The gas pressure also moves a plunger downwardly to force the medication through the needle. After the gas escapes, the diaphragm returns to its normal position, withdrawing the needle.
Many drug delivery devices utilize stored energy to insert the needle into the patient and deliver the medication. This energy can be stored in the form of material resiliency, compressed springs, magnets, batteries, pressurized gas, or chemical reaction. A combination of these components may be utilized, along with other mechanical components such as ratchets, levers, and hinges. These various moving parts and energy sources can be complicated for the patient to use.
Accordingly, there is still a need for a medication delivery device that is simple to use and enables the patient to safely inject a needle, deliver a desired dose of medication, and dispose of the used needle without professional medical assistance.